Iron alloy for cutting tools



Patented Nov. 4, 1941 2,261,851 IRON ALLOY FOR CUTTING TOOLS LeoKliiger. Vienna, Germany, asslgnor to Fcmr Steel Corporation, of

Applicati In No Drawing.

rial No. 238,026. 1937 Lnxemburg on October 31, 1938, se-

Germany November 3,

1 Claim. (Cl. 75126) It has previously been proposed to make cuttingtools, drills, reamers, milling and other tools, which must be made ofspecially hard material, from iron alloys which are capable of beingcast and flow easily, the rough casting being substantially in the finalshape required. These alloys have a somewhat high carbon content inorder to ensure the fluidity necessary for casting; they also containadditions of tungsten, molybdenum and chromium. It has been found,

however, that the behaviour of these steel alloys is such that theycannot be widely used in practice.

The cutting speed of these steels can not be increased up to that ofhigh speed steels because the surface of the object to be machined isthen not smooth but becomes wavy to some extent and a subsequentgrinding process is necessary. that these alloys must it has also beenfound be hardened at high temperatures and the parts of the tool whichare subjected tothe greatest stress, namely the cutting edges, will notwithstand such high temperatures but fuse away. Finally, it has alsobeen found that erosion of the cutting edge takes place at red heatduring working, for example during milling.

All these disadvantages are obviated when tools made of alloys inaccordance with the present invention are used. In the alloys accordingto the invention a definite relationship is maintained between chromiumon the one hand and the sum of all the other selected alloy additions onthe other hand. Particular attention is drawn to the fact that millingcutters and other tools which are made from these alloys can be cast tothe finished dimensions, ground andoperated at high cutting speeds,notwithstanding which the machined surface remains quite even and smoothand does not require to be subsequently smoothed or ground as usual.

An'alloy in accordance with the invention may consist for example of 6%chromium, 1% t1mgsten, 1% molybdenum, 1% cobalt, 0.5% manganese. 0.5%vanadium, carbon in an amount up to 1.5%, and the remainder iron. Inthis alloy the weight of the tungsten, molybdenum, cobalt,

manganese, vanadium, and carbon amounts to substantially 92% of theweight of the chromium when the alloy contains '1.5% carbon.

A feature which is essential if the alloys are to have the propertiesdesired is that the sum of all the metallic and metalloid constituentsexcluding chromium amounts to or more of the chromium content of thealloy. The parts by weight of the constituents contained in the alloycan therefore be varied, for example, 'in accordance with the followingtable without departing from the condition stated above and withoutimpairing the usefulness of the alloy for the purpose in question.

Cr W0 Mo .00 Mn Ya Percent Percent Percent Percent Percent Percent 6. 0.l. 8 0. 6 1. 2 8.0 2.4 p 0.8 1.6 10.0 4.0 0.5 3.0 0. 5 0. 5

In the above table the weight of the alloying elements, other thanchromium, ranges from 60% to of the weight of the chromium.

drills and the like can be cast alloys do not contract greatly underheat treatment.

in their final shape. and expand very They also become speeds isensured; also the cutting edges do not fuse away. A milling cutter madeof an alloy in accordance with the invention produces a tent diilersfrom that given in the examples also fall within the invention providedthe relationship between the chromium content and the sum of theremaining metallic or metalloid additions is maintained. I claim:

A steel alloy, tools, containing Mo about 0.5%, Va about 0.5%, theremainder Cr about 10%, W0 about 4%. Co about 3%, Mn about 0.5%, C in anamount up to 1.5%. and Fe.

LEO KLUGER.

alloys flow easily so that milling cutters, I

adapted to be cast, for cutting

